any other info you can provide? like, what are the sql statements that cause it?

As you can see, the load on the machine changes by mid of june. This is the time when the new release was installed:

While the workload by queries is "constant":

There was no change in the webapps using the database.

Unfortunately, it doesn't help much, this simply repeats what you said above, "update from 10.5.15 to 10.5.16 I can see ~double of cpu usage".

What kind of sql statements do your webapps use? Can you show an example of a statement that use more CPU or take longer after the upgrade? May be a general query log or SHOW PROCESSLIST could help to get a sample of the load.

maybe this is all caused by #27883
there are not much slow queries, or anything I can see from processlist. I assume e.g. optimizer uses more cpu but not noteable on a single query. At the moment this does not affect me much - but the higher cpu load can be observed. But I don't have a good clue how to give you more (relevant) information.